Here, we see two drawings of the myoglobin molecule that binds to iron and oxygen in muscle tissue. The iron bound to myoglobin is what gives meat its red color. The iron is bound to a central ring structure, which is surrounded by a long chain of amino acids that fold around the central ring in a series of helices. The drawing on the left is an accurate sketch of the ring surrounded by helices. On the right, we see what this molecule looks like in a space-filling diagram: a very complicated blob. (Unit: 9)